You might feel as though your joint is "giving way" or weakening. Your joint might pop or stick in one position if a loose fragment gets caught between bones during movement. The skin around your joint might be swollen and tender. This most common symptom of osteochondritis dissecans might be triggered by physical activity - walking up stairs, climbing a hill or playing sports. The MRI also has the advantage over both plain radiographs and computed tomography (CT) scanning in its ability to detect the true Stage I lesion where the only finding may be edema in the body of the talus without a discrete bony lesion.Depending on the joint that's affected, signs and symptoms of osteochondritis dissecans might include: They tend to mimic the plain radiographic evaluation suggested by Berndt and Harty ( 3), but add the evaluation of the cystic component which is present in may of the osteochondral lesions ( Table 49-2). Several classification schemes for MRI evaluation have been suggested ( 8). Because the MRI is very sensitive inÄetecting bone edema, it may actually overestimate the size of the lesion. If an osteochondral lesion is noted on plain radiographs, the MRI may be useful in evaluating the lesion itself for articular cartilage congruity, whether there is fluid signal beneath the bony fragment to suggest a loose lesion and to evaluate the degree of edema in the surrounding talus. MRI is sensitive in detecting osteochondral lesions of the talar dome and may also aid in the evaluation of other soft tissue and bony entities on the differential diagnosis. In the absence of a discrete lesion on plain radiograph, MRI examination is the most appropriate follow-up examination for patients with persistent symptoms despite a period of nonoperative management. Stauffer ( 7) refined the biomechanical explanation of causation of these lesions, suggesting that relatively small tangential or shear forces resulted in bony fracture with the articular cartilage remaining intact, whereas failure of both bone and articular cartilage occurs with application of larger forces. In contrast, when the externally rotated ankle was in a plantar flexed position, inversion of the joint resulted in physical contact of the posteromedial talar dome with the tibial articular surface. Although their numbers were very small (only a total of three lesions were created in a total of 15 ankles), their study suggested that the lateral lesion resulted when the anterolateral talar dome impacted the articular surface of the fibula with the ankle in a dorsiflexed position. The medial lesion could be produced when the plantarflexed foot was subjected to an inversion force. The lateral talar dome lesion could be produced with a combination of ankle dorsiflexion and inversion. This is the theory supported by the early study of Berndt and Harty ( 3) where a small number of talar dome lesions were created in cadaver ankles by applying inversion or eversion forces combined with ankle dorsi or plantar flexion. The repetitive trauma events may be in the form of recurrent ankle sprains, where joint deformation causes direct impact of the talar dome on the adjacent tibia or talus. They can occur after a single specific injury, or be the result of repetitive microtrauma. Most studies have suggested that the lesions are traumatic in nature. In addition, although the lateral lesions are usually unilateral, the medial lesions are found to be bilateral in up to 10% of patients ( 2). The more chronic nature of the medial lesions along with the absence of a definite traumatic association with many medial talar dome lesions supports the possibility that they are either due to low level repetitive trauma or perhaps to another cause such as avascular necrosis, steroid use, embolic event, endocrine abnormality, or hereditary factors ( 6). The patients with medial lesions tend to present with more chronic symptoms of ankle pain rather than an acute injury, and are found to have an osteochondral lesion on plain radiograph or magnetic resonance imaging (MRI) of the ankle. The vast majority of lateral lesions are associated with a distinct traumatic episode and patients frequently present with an acute injury and positive radiographic findings. The medial lesions tend to be deeper and cup shaped whereas the lateral lesions tend to be thinner and more wafer shaped ( 2). Although osteochondral lesions can occur over any portion of the talar dome or the tibia, the talar lesions typically occur over the anterolateral or the posteromedial talar dome.
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